a standard bi metal hole saw will cut mild steel many, many times IF used right. when making my own 14FF caliper brackets I cut 3 3/4 dia. holes using a 3 3/4 hole saw through 1/2 in steel in a mill with a flood of cutting oil with ease. I ran it as slow as a mill will turn, 60 rpm and I pecked the cut clearing the chips very often, but it cut easy.
no more then 10 min. a complete cut, and the hole saw is still sharp, even after 4 cuts through 1/2 in steel.
the problem with cutting by hand with a drill motor is you tend to run the saw too fast, and with a inconsistant rpm. even stoping the saw in the cut which is brutal on ANY cutting teeth on ANY KIND of cutter, which just dulls the saw prematurely. try as you may, its hard to keep a hole saw at a CONSISTANT rpm. also when using a drill you only put minimal cutting fluid on the saw. because your busy sawing ofcourse. it requires as much as you can get on it. this is exactly the reason why cnc machines have flood coolent capability.
as decribed in other discussions about cutting tools heat is the killer of a cutting tool. for this reason alone you MUST flood a saw, especially if its of a decent size with cutting fluid. remember, a saw 2 in larger at the same drill rpm in actually turning a much greater rpm then the one thats smaller. its turning more surface per minute. this is what creating the excessive heat which is wearing out the saw prematurelly. do not stop a saw in the cut. putt it out of the cut first. use LOTS of cutting oil. dont over rpm it. clear your chips often if its thick material. use a good amount of "feed".
if it is chattering its too much rpm or not enough feed pressure. to light of feed again creates too much heat and is just wearing the hell out of the tooth edge. a tool works properly when its cutting, NOT rubbing. any brand name saw in good, I have used them all. Lenox, Starrett, Millwaukie, Morse, what ever. that concludes this cutting lesson for today

. I could go on and on and on and.......